1. Field of the Invention
The present invention relates to a pretensioner that increases tension of a webbing belt configuring a seatbelt device of a vehicle in a vehicle rapid-deceleration state or the like.
2. Related Art
In a pipe for pretensioner (a configuration corresponding to the pipe is called “cylinder” in the present invention) disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2004-1656, a seamless pipe which will to be a pretensioner pipe is subjected to pipe-expanding, thereby an inner diameter dimension of the pipe is partially expanded in order to form a portion for accommodating a gas generator, the region having a large inner diameter dimension compared with other regions.
Since a seamless pipe is subjected to such pipe-expanding, and thereby wall thickness of the seamless pipe may be partially changed, so mechanical strength of a pretensioner pipe may be partially changed. However, in such pipe-expanding, since the seamless pipe is pressurized from the inside to the outside of the pipe so that an inner diameter dimension is increased, so an outer diameter dimension is also changed. Therefore, a specification of a frame of a webbing winding device, the frame being mounted with a pretensioner pipe, needs to be changed for each specification of an inner diameter dimension of a pretensioner pipe, leading to low wide-usability.